I've tie-dyed favourites after similar accidents, usually just tieing pinches with string and moving it round in a bucket, maybe a quarter-mug of bleach in lukewarm water until it's a good colour, never left it overnight, more an hour or so as I remember.An alternative is using white embroidery thread (silk) and white fabric dye to make a simple pattern round the bleached bit, then adding more of similar design on both sleeves, if you like relaxing sewing jobs. (Had similar accidents before).